1. Field of the Invention
The present invention relates to an ignition apparatus for an internal combustion engine and particularly to an ignition apparatus, for an internal combustion engine, that makes a pulse current with an alternating polarity recurrently flow so as to increase ignition energy.
2. Description of the Related Art
In a spark-ignition internal combustion engine, an ignition apparatus configured with an ignition coil and the like produces an ignition discharge between the electrodes of an ignition plug, and due to the ignition discharge, a fuel introduced into a combustion chamber is burned. There is proposed a multiple-discharge ignition apparatus in which, in order to obtain a preferable combustion state of the internal combustion engine, a plurality of ignition discharges is produced between the electrodes of an ignition plug during a single combustion stroke.
For example, an ignition apparatus is configured in such a way that there are provided an energy storing coil connected in series with a DC power source and a first switching means connected in series with the energy storing coil, the energy storing coil and a second switching means are connected with the primary coil of an ignition coil, and an ignition plug is connected with the secondary coil of the ignition coil. Additionally, there is proposed an ignition control apparatus, for an internal combustion engine, in which the first and second switching means are alternately turned on/off so that charging and discharging of the energy storing coil are recurrently carried out, and through the charging and discharging, a current with a positive-negative alternating polarity is recurrently made to flow in the secondary coil of the ignition coil so that multiple discharge is performed (for example, Japanese Patent Application Laid-Open No. 2007-211631 (claims and FIG. 1).
However, in an ignition apparatus for an internal combustion engine proposed in Japanese Patent Application Laid-Open No. 2007-211631 (claims and FIG. 1), there has been a problem that a desired current cannot stably flow in the ignition plug, depending on the voltage of a DC power source connected in series with the energy storing coil, whereby erosion on the ignition plug is caused or ignition operation becomes unstable.